There has been proposed a known color image reading apparatus including an LED capable of emitting three primary colors of R (red), G (green) and B (blue). The known color image reading apparatus emits R light, G light and B light by the LED to a sheet in sequence and reads the sheet. To simplify control an R-light source, G-light source and B-light source of the LED, the known color image reading apparatus sets current values of the R-light source, G-light source and B-light source to the same and adjusts emission times of the R light, G light and B light individually to appropriate values for setting light amount in reading the sheet.
One known image reading apparatus, which includes a pair of LEDs, adjusts a light emission time of one LED based on an end of a light emission period of one line cycle and adjusts a light emission time of the other LED based on a start of the light emission period of one line cycle in order to shorten a time period where the light is not emitted to a sheet.
Another known image reading apparatus includes a plurality of light source units for emitting light to a sheet in order to increase amount of light reflected from the sheet.